The invention relates to a device for adjusting and fixing the relative position between an actuator end piece of an active hearing implant on the one hand and on the other hand, an element of the ossicular chain or a coupling part to the human inner ear, in particular to the perilymph of the labyrinth system or to the endolymphatic compartment; the device is equipped with a connecting element having a first coupling element for coupling the connecting element to the actuator end piece, having a second coupling element for coupling the connecting element to the incus, the stapes, the stapes footplate, the oval window, or the round window of the human middle ear, and having a shaft-shaped middle part between the first coupling element and the second coupling element.
Such a device for adjusting and fixing the relative position of two elements of an active hearing implant is known from U.S. Pat. No. 5,941,814.
In the event of partially or entirely missing or damaged ossicles of the human middle ear, hearing implants are used to transmit the sound, which strikes the outer ear, or a corresponding audio signal to the inner ear. In this context, a distinction is drawn between passive ossicular prostheses on the one hand that physically replace parts of the ossicular chain, with the transmission of sound occurring “passively,” i.e. without assistance from electronic aids, and active hearing implants on the other hand that receive electrical signals, which correspond to the audio signals, from an electronic amplifier of a hearing aid worn outside the middle ear, transmitted via an actuator implanted in the middle ear, convert them through mechanical motion back into acoustic oscillations and transmit them from a vibrating actuator end piece into the inner ear via a suitable connecting element. Such active hearing implants—and in particular, the problem of an optimal acoustic coupling of the actuator end piece to the inner ear—are the subject of the present invention.
The diameter of the generally cylindrical actuator end piece is usually standardized, i.e. is always the same size or is at least provided in a group of particular discrete sizes from which a selection is made in association with the different individual circumstances of the individual patient.
DE 200 14 659 U1 has disclosed a device for adjusting and fixing the relative position between the actuator end piece (“actuator”) of an active hearing implant on the one hand and an element of the human ossicular chain on the other hand. In this context, the known device is equipped with a connecting element having a first coupling element in the form of a receptacle with clamps for coupling to the actuator end piece, having a second coupling element in the form of a clip for coupling to the stapes, and having a shaft-shaped middle part between the first and second coupling elements.
In U.S. Pat. No. 5,941,814, which was cited at the beginning, as a first coupling element for coupling the connecting element to the actuator end piece, a crimping sleeve embodied in the form of a hollow cylinder is proposed, through which the actuator end piece is inserted during the implanting operation and then permanently fastened by being cold caulked with a crimping tool. Between the outside of this crimping sleeve and the shaft-shaped middle part, there is a rigid mechanical connection, for example produced by means of a spot weld or soldering point.
One problem with this known geometric arrangement is the lack of flexibility for an exact relative spatial positioning between the vibrating actuator end piece and the first coupling element of the connecting element in the middle ear. Sliding the first coupling element a greater or lesser distance into the cylindrical cavity of the crimping sleeve does in fact achieve a certain amount of variability in the direction of the cylinder axis of the crimping sleeve. However, there is no possibility whatsoever of adjusting in a direction perpendicular to this cylinder axis so that the fine three-dimensional positioning of the connecting point between the actuator end piece and the first coupling element and therefore a precise fixing of the final position of the entire device can only be carried out in an extremely imprecise fashion.
This correspondingly leads to undesirable stresses within the implant structure and therefore to less than optimal geometric adaptation of the relative positions of the individual connecting pieces, which finally in turn results in a significantly poorer frequency response of the entire hearing implant and less of an improvement in the sound conduction than the entire device with the active hearing aid is actually capable of from a technical standpoint.